Zn-Assisted Mg Ion Transport in Spinel Oxide Cathodes: Insights From Neural Network Simulations

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Developing high-performance magnesium batteries requires understanding ion transport mechanisms.
• Defect spinel structures offer potential for enhanced ionic conductivity.

Purpose of the Study:

• Investigate Mg insertion and ion transport in MgxZnyMnO3 defect spinels.
• Determine the relationship between composition, structure, and Mg diffusion.
• Identify optimal compositions for improved magnesium battery performance.

Main Methods:

• Utilized a neural network potential for accurate energy calculations.
• Employed molecular dynamics simulations to study ion transport.
• Applied genetic algorithm-based structure exploration to discover stable phases.

Main Results:

• Mg diffusion coefficients vary significantly with composition (x).
• Stoichiometric spinel (x=0.25) and rock-salt (x=1.0) phases show very low conductivity.
• Enhanced Mg diffusivity observed in cation-deficient (x<0.25) and cation-excess (0.25
• Zn2+ ions consistently diffuse faster than Mg2+ ions.
• Biphasic spinel-rock-salt coexistence is favored for 0.25

Conclusions:

• Stoichiometric phase precipitation can hinder Mg transport and battery capacity.
• Solid-solution pathways are kinetically accessible, offering routes for improved Mg mobility.
• Zinc plays a crucial role in stabilizing sites and enhancing Mg mobility.
• Findings provide design guidelines for high-voltage and high-diffusivity magnesium battery cathodes.